The present invention relates generally to a bolster for use with a rail truck assembly. The bolster having a spring top receptacle comprising a plurality of spring pockets for engaging and retaining load springs in an aligned, spaced relation and predetermined arrangement. The spring receptacle for receiving the tops of springs, mounted on a respective side frame, to help with installation and to prevent the springs from becoming misaligned due to rough rail conditions.
In the railway rolling stock art, it is common practice to support the opposed ends of a freight railcar body on spaced-apart wheel-truck assemblies for travel along a railway track. A standard railcar wheel-truck assembly generally has a laterally spaced pair of side frames that are longitudinally operable along the trucks and parallel to the longitudinal axis of the railcar. A bolster, which is transversely positioned to the longitudinal direction of the railcar, couples the side frames and has the freight car body supported on bolster center plate section. A railcar wheel-truck or truck positioned at opposing ends of the railcar support the railcar during its traversal of the rail track.
Each side frame includes a window portion for receiving the bolster ends and a spring group on the side frame supporting the bolster. This structure allows bolster movement relative to the side frame. Each spring group typically includes a plurality of coil springs compressed between a side frame and the bottom of the bolster end. The bolster end is supported in spaced relation to the support platform. Elastomeric spring type products may also be utilized in a spring group as an alternative to the coil springs.
Railway track conditions can include rail running surface variations or discontinuities from differential settling of track on its ballast, rail wear, corrugations, rail misalignment, worn switch frogs or misaligned switch points, switches where switching points match with running rails, and rail joints. During normal railcar usage or operation, these and other variations can result in wheel-truck oscillations, or vibrations which may induce the railcar body to bounce, sway, rock or engage in other unacceptable motions. Wheel-truck movements transferred through the suspension system may reinforce and amplify the uncontrolled motions of the railcar from track variations, which action may result in wheel-truck unloading and a wheel or wheels of the truck may lift from the track. This unloading may cause the spring groups to disengage contact with the side frame or the bolster. The disengagement may cause the springs to fall out, become misaligned or tangled. The loss of a spring will create a dangerous situation by not having enough spring capability to support the load of the rail car. Misaligned or tangled springs may rub causing weak spots on the springs leading to a spring break creating a dangerous condition concerning supporting the rail car.
The American Association of Railroads, the AAR establishes a very severe criterion for railcar stability, wheel loading, and spring group structure. These, criteria are set or defined in recognition that railcar body dynamic modes of vibration, such as rocking of sufficient magnitude, may compress individual springs of the spring group at alternate ends of the bolster, even to a solid or near-solid condition. This alternate-end spring compression is followed by an expansion of the springs, which action-reaction can amplify and exaggerate the ‘apparent’ wheel loading on the suspension system and subsequent rocking motion of the railcar, as opposed to the actual or “average” weight or load from the railcar and freight therein. Because of the amplified rocking motion, and at large amplitudes of such rocking motion, the contact force of the load springs between the bolster and the side frame can be dramatically reduced on the alternate lateral sides of the railcar. In an extreme case, the springs can come loose and shift positions and tangle control springs with load spring. A misaligned or tangled spring enhances the opportunity for spring failure, derailment or increased maintenance.
There are various modes of motion of a railcar body, which is bounce, pitch, yaw, and lateral oscillation, as well as the above-noted Roll. In car body roll, or twist and roll as defined by the AAR, the car body appears to be alternately rotating in the direction of either lateral side and about a longitudinal axis of the railcar. Car body pitch is considered a forward to rearward rotational motion about a transverse railcar axis of rotation, such that the railcar may appear to be lunging between its forward and reverse longitudinal directions. The above-noted car body bounce refers to a vertical and linear motion of the railcar. Yaw is considered a rotational motion about a vertical axis extending through the railcar, which gives the appearance of the car ends moving to and fro as the railcar moves down a track. Finally, lateral stability is considered an oscillating lateral translation of the car body. Alternatively, truck hunting refers to a parallelogramming or warping of the railcar truck, not the railcar body, which is a separate phenomena distinct from the railcar body motions noted above. All of these motion modes are undesirable and can lead to unacceptable railcar performance, as well as contributing to unsafe operation of the railcar. All can be the result of inadequate or faulty spring support between the side frame and the bolster. The challenge in the suspended support of the rail car on the load springs includes maintaining the springs in an optimum position with respect to the other springs between the side frame and the bolster and keep spring separated to prevent hang up of control springs on load springs. Therefore, a need exists to separate and hold the springs in a desired alignment and support position.